PROJECT SUMMARY AND ABSTRACT Colorectal cancer (CRC) is the second leading cause of cancer death in the US. Despite overwhelming evidence that screening reduces both CRC incidence and mortality, less than two-thirds of eligible adults are up-to-date with screening. These figures also overestimate the proportion of Americans who receive adequate long-term protection from CRC because they are based on one-time, cross-sectional measurements. To ensure that eligible populations receive maximal benefit from CRC screening, it is critical to accurately measure adherence to different screening strategies over multiple cycles, to identify the various barriers to repeated screening, and to translate this information into effective interventions that can be implemented rapidly and efficiently. This K08 proposal will address the following three specific aims: (1) Quantify longitudinal adherence to screening colonoscopy and FOBT/FIT in the national VA database over a 15-year period; (2) Identify social and contextual barriers and facilitators to longitudinal adherence using a qualitative approach in veterans who are due for repeat screening/surveillance colonoscopy at an urban VA hospital; and (3) Assess the feasibility of a pilot bidirectional text messaging intervention on attendance for screening/surveillance colonoscopy and bowel preparation quality. This will be the first study to compare longitudinal adherence to screening colonoscopy and FOBT/FIT and one of the first to investigate the influence of text messaging on colonoscopy adherence. This award will allow the PI to obtain additional training in quantitative and qualitative methods, behavioral intervention design, and mHealth. Findings from the proposal will provide important insight into the optimal long-term CRC screening strategy and methods to improve adherence to repeat screening. This will form the foundation of a subsequent R01 grant and help the PI develop into an independent investigator.